This invention relates to an apparatus for regulating fiber quantities supplied to at least one carding machine. The apparatus has a pressure measuring member installed in a pneumatic supply and distributor duct upstream of the carding machine. The pressure signals are converted into electric signals (actual pressure magnitudes). The output of the pressure measuring member is coupled via a regulator to a regulated drive of a fiber tuft supply apparatus, such as a fiber cleaner.
European Patent No. 0 303 023, to which corresponds U.S. Pat. No. 4,940,367 describes an arrangement in which the fiber quantities of a card feeder are regulated based on a nominal value/actual value comparison, as a function of which the rpm of an upstream-disposed opener is varied. Because of the fiber quantity already present in the conduit after regulation is initiated (fiber material lag), such a regulating method results in pressure fluctuations in the card supply which, in turn, affect the fiber batt density in the card feeder. To obtain an optimal, uniform batt density, pressure fluctuations should be kept at a minimum. Since the deviation of the pressure from the set nominal pressure is a measure for the deviation of the material intake speed of the opener from a preset mid value, to each pressure value a fixed rpm value is associated. In case of substantial deviations, upon reaching the nominal pressure value based on the above-described material lag, a significantly excessive or insufficient output takes place. As a result, the pressure signal over-regulates and thus the undesired fluctuations take place. In case the number of the carding machines is reduced during operation, for example, by shutting off one of the cards, the supply and distributor duct is shortened which results in an increased static pressure. Such an increased actual pressure value at the pressure measuring member leads to an immediate change of the quantity of the fiber tufts discharged by the cleaner, that is, it leads to a reduction of the fiber quantity feed which is sufficient for the cards that continue to operate. However, the fiber quantities introduced into the conduit before the initiation of regulation (that is, the change of the intake speed of the cleaner) are still in the conduit. It is a disadvantage that such a large tuft quantity leads to a further increase in the static pressure due to the resistance of the fiber material (because of the reduced cross section at the air outlet openings) which, in turn results in a further reduction of the fiber feed quantities below the predetermined value. It is a further drawback that the lag represents an excessive fiber quantity for the cards still operating. The above-discussed problems occur not only upon the stoppage of one of the carding machines but because of the fluctuating fiber quantity requirements by all operating carding machines.
It is an object of the invention to provide an improved apparatus of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, makes possible a uniform fiber tuft feed even at substantial deviations of the pressure and/or the fiber quantities due to the changing material requirements by the after-connected carding machines.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for regulating fiber quantities to be supplied to a carding machine includes a duct in which the fiber material is pneumatically advanced; a feed mechanism to advance fiber material to the duct at a variable flow rate; a regulator connected to the feed mechanism for varying the flow rate; a pressure sensor disposed in the duct; an arrangement for generating first electric signals representing actual pressure values detected by the pressure sensor; an arrangement for differentiating the first signals over time to obtain second electric signals for correcting the first electric signals to obtain third electric signals representing corrected actual pressure values; and an arrangement for applying the third signals to the regulator for varying the flow rate of the fiber material, advanced by the feed mechanism, as a function of the signals.
The setting member (that is, the drive for the material intake rolls of the upstream connected cleaner) is set even before a change of pressure in the fiber supply duct occurs. Based on the slope of the pressure curve as a function of time, the increasing, constant or decreasing pressure values (as viewed over time) are xe2x80x9canticipatedxe2x80x9d and thus the feed of the fiber tufts is accordingly set. The increase of the pressure signal is obtained by a xcex94p/xcex94t differentiation. This increase is used to additionally affect the intake velocity of the opener. The fixed association of the intake velocity with the pressure signal is thus partially discontinued since in case of increasing pressures a smaller intake speed is assigned than in case of dropping pressures. The momentary pressure value thus does not by itself predetermine the intake velocity. In this manner a damping of the pressure signal may be obtained.